1. Field of the Invention
The present invention relates to a chucking mechanism of a center core of a disk cartridge to receive a drive spindle, the center core being fixed to the center of a disk, which serves as a recording medium and is rotatably housed in a housing of the disk cartridge, which is of the type that is employed in a disk drive provided with the drive spindle.
2. Description of the Related Art
Recording media, e.g., a micro-magnetic disk cartridge called “clik! (registered trademark)” have been conventionally used for mobile equipment such as digital cameras.
FIGS. 4A to 4C are a plan view, a right side view and a bottom plan view of a magnetic disk cartridge 1, respectively. As shown in these Figures, a flat housing of the magnetic disk cartridge 1 rotatably contains a magnetic disk 5. The flat housing is constituted of a resin frame 2 which includes a pressing portion 2a, and upper and lower shells 3 and 4 which are made of thin metal plates. The dimensions of the housing are 50 mm wide by 55 mm deep by 1.95 mm thick. The magnetic disk 5 has a storage capacity of 40 MB and a diameter of 1.8 inches (45.7 mm).
The magnetic disk cartridge 1 is constituted so as to be inserted and placed into a slot of a Type II PC card drive which has the dimensions of 53 mm wide by 85 mm deep by 5 mm thick. This disk drive is provided with a spindle motor and a magnetic head. The spindle motor includes a drive spindle which magnetically attracts a center core 10 of the magnetic disk 5, and the magnetic head which accesses to the surface of the rotating magnetic disk 5 to record and reproduce information.
A V-shaped opening 6 is formed in the housing of the magnetic disk cartridge 1 for the magnetic head of the disk drive to access the surface of the magnetic disk 5. A rotary shutter 7, which is urged toward a closed position by a spring member, opens and closes the opening 6. The rotary shutter 7 is locked at a closed position shown in FIGS. 4A and C by a shutter locking member 11 provided in the housing.
A notch 8 is formed on the top portion of the left side of the housing to engage with an engaging member of the disk drive to ensure the positioning of the magnetic disk cartridge 1 in the disk drive. On the top portion of the right side surface, a small window 9 is formed so that the shutter locking member 11 faces outside. The shutter locking member 11 is constituted to be pressed by a lock releasing member provided in the disk drive to release the lock on the rotary shutter 7 when the magnetic disk cartridge 1 is inserted into the disk drive.
A circular opening 4a and an arcuate groove 4b are formed in the lower shell 4 of the housing. The opening 4a is for the drive spindle of the disk drive to engage with the center core 10 of the magnetic disk 5, and the arcuate groove 4b is concentric with the rotary shutter 7. A shutter knob 7b is attached to the rotary shutter 7. The shutter knob 7b protrudes from the arcuate groove 4b and moves along the arcuate groove 4b to open and close the rotary shutter 7.
FIG. 5 is a sectional view showing the center core 10 as well as a drive spindle 20. The center core 10 provided with a center aperture 10a is formed from an iron based metal material. The magnetic disk 5 is affixed to a flat upper surface 10b (adhesion surface) of the center core, and a bottom surface 10c (engaging surface) engages with the drive spindle 20.
Meanwhile, the drive spindle 20 is provided with the main body of a spindle 21 and a magnet 22. The main body of the spindle 21 is the core, and the magnet 22 magnetically attracts the center core 10. A flat upper surface 21a (engaging surface) of the main body of the spindle 21 engages with the center core 10. The drive spindle 20 is constituted as follows: when the magnetic disk cartridge 1 is placed in the disk drive, the magnet 22 attracts the center core 10 onto the main body of the spindle 21; and the center core 10 engages with the drive spindle 20 in a state where the surfaces 10c and 21a are in contact with each other.
However, in the case where the center core 10 and the drive spindle 20 are engaged in a state where the surfaces 10c and 21a are in contact as described above, there were times when the center core 10 was engaged with the drive spindle 20 in a slanted state, when the surface precision of the engaging surface 10c of the center core 10 is low. In this case, parallelism between the rotation surface of the drive spindle 20 and the rotation surface of the magnetic disk 5 is reduced. Accordingly, wobbling of the magnetic disk 5 surface increases when the drive spindle 20 rotates. Thus, there has been a problem that recording/reproducing characteristics are aversely affected.
Moreover, it is extremely difficult to maintain the surface precision of the engaging surface 10c of the center core 10. This has been reducing the material utilization rate for the center core 10 and increasing manufacturing costs of the center core 10.